core: generic_boot: Add add_dt_overlay_fragment()

This patch adds a dt routine add_dt_overlay_fragment(). This purpose of
which is to encapsulate the dynamic FDT node entries OPTEE provides inside
of a

fragment@0 {
        target-path = "/";
        __overlay__ {
                /* OPTEE nodes go here */
        };
};

A subsequent set of patches will wrapper up existing dynamic OPTEE nodes

- /firmware/optee
- /psci
- /reserved/memory
      optee@0xaddress

Once done it will be possible for a DTB in memory to be populated
with OPTEE fragments and for a subsequent bootloader to merge the OPTEE
populated overlay into a DTB loaded by a later stage.

if CFG_EXTERNAL_DTB_OVERLAY is not defined then this code has no effect.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/core/arch/arm/kernel/generic_boot.c b/core/arch/arm/kernel/generic_boot.c
index e1c59a06..d31976da 100644
--- a/core/arch/arm/kernel/generic_boot.c
+++ b/core/arch/arm/kernel/generic_boot.c
@@ -76,6 +76,9 @@ KEEP_PAGER(sem_cpu_sync);
 #ifdef CFG_DT
 extern uint8_t embedded_secure_dtb[];
 static void *dt_blob_addr;
+#ifdef CFG_EXTERNAL_DTB_OVERLAY
+static int __dt_frag_id;
+#endif
 #endif
 
 #ifdef CFG_SECONDARY_INIT_CNTFRQ
@@ -484,6 +487,33 @@ static void reset_dt_references(void)
 	dt_blob_addr = NULL;
 }
 
+#ifdef CFG_EXTERNAL_DTB_OVERLAY
+static int add_dt_overlay_fragment(void *fdt, int ioffs)
+{
+	char frag[32];
+	int offs;
+	int ret;
+
+	snprintf(frag, sizeof(frag), "fragment@%d", __dt_frag_id);
+	offs = fdt_add_subnode(fdt, ioffs, frag);
+	if (offs < 0)
+		return offs;
+
+	__dt_frag_id += 1;
+
+	ret = fdt_setprop_string(fdt, offs, "target-path", "/");
+	if (ret < 0)
+		return -1;
+
+	return fdt_add_subnode(fdt, offs, "__overlay__");
+}
+#else
+static int add_dt_overlay_fragment(void *fdt __unused, int offs)
+{
+	return offs;
+}
+#endif /* CFG_EXTERNAL_DTB_OVERLAY */
+
 static int add_dt_path_subnode(void *fdt, const char *path, const char *subnode)
 {
 	int offs;